Waterloo, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.1 °C (low) to 14.2 °C (high). Annual precipitation averages 974.4 Millimeters. Waterloo is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -12.5 °C | -3.1 °C | 28.45 mm |
| February | -10.2 °C | -0.6 °C | 30.73 mm |
| March | -3.8 °C | 6.8 °C | 53.09 mm |
| April | 2.7 °C | 14.9 °C | 104.14 mm |
| May | 9.6 °C | 21.4 °C | 123.19 mm |
| June | 15.6 °C | 26.8 °C | 145.29 mm |
| July | 17.2 °C | 28.5 °C | 122.17 mm |
| August | 15.7 °C | 27.4 °C | 107.7 mm |
| September | 10.8 °C | 24.1 °C | 92.46 mm |
| October | 4 °C | 16.6 °C | 75.95 mm |
| November | -2.8 °C | 7.6 °C | 51.31 mm |
| December | -8.7 °C | 0.3 °C | 39.88 mm |
| Annual | 3.1 °C | 14.2 °C | 974.36 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |